Avalanche Forecast

Issued: Dec 21st, 2011 8:52AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

mpeter, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Due to variable snopack conditions

Weather Forecast

Thursday: Expect dry conditions with mostly clear skies. Winds should be westerly and reach 40-60 km/h at ridgecrests. Freezing levels may reach 1300m. Friday: Dry conditions persist with continued westerly winds and freezing levels reaching 1500m. Saturday: Winds turn southwest and increase to 60-80km/h at ridgecrest with freezing levels climbing as high as 1800m.

Avalanche Summary

We have isolated reports of shallow slab avalanches affecting the top 20 cm of the snowpack, running on the mid-December surface hoar layer in the northern part of the region.

Snowpack Summary

Westerly winds continue, creating windslabs on lee locations in the alpine and open treeline. A buried layer of surface hoar lies approximately 20 cm below the snow surface. Reports indicate this layer was blown around before it was buried and can only be found in isolated, sheltered locations. A well settled mid pack bridges over the basal weaknesses at the ground. This layer was responsible for some large releases earlier on in the season. However, there hasn't been any activity on this layer since early December and confidence is growing that it is gaining strength.

Problems

Wind Slabs

Shifting winds have set up wind slabs on a variety of aspects, especially on north through southeast aspects. Watch out for cross-loading on open slopes oriented parallel to the wind direction too.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Thin slabs are beginning to become reactive on the mid-December surface hoar layer. In places, these relatively low mass events have been running fast and far.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 22nd, 2011 8:00AM